Topic overview

Start with the big picture

The lesson introduces pH as a measure based on hydrogen ion activity and connects pH changes with drug solubility, ionization, membrane permeability, and chemical stability. The Henderson–Hasselbalch relation helps describe the balance between ionized and unionized drug forms and informs formulation choices. You will examine how weak acid/base buffer pairs resist changes in pH, why buffer capacity depends on pH relative to pKa and concentration, and how common systems such as acetate, citrate, phosphate, bicarbonate, and TRIS are used. Pharmaceutical applications include parenteral, ophthalmic, and oral products, alongside physiological buffering. The topic also introduces incompatibilities, safety considerations, and regulatory documentation.